Millennium Telescope Project

Aperture Fever…!

Objectives Build large aperture portable telescope Maximise light gathering ability Lightweight open tube design Transportable to deep sky locations

Obsession 20” F/5 Completed scope

Babcock 24 inch

Design Goals Ease of construction Ease of assembly/disassembly Ease of storage and transportation Ease of collimation (repeatable)

MMT Activities...

Mirrors Primary Mirror (Pyrex): –Diameter, 482 mm(19”) –Edge thickness, 38 mm(1.5”) –Focal length, 2165 mm (F/4.5) –Calculated weight 15.6 kg (34 lb) Secondary Mirror (elliptical plate glass): –Major axis, 150 mm(5.9”) –Minor axis, 106 mm(4.2”) –Thickness, 14.5 mm(0.6”)

Component Weights Primary Mirror15.39 kg (33.9lb) Mirror cell base5.48 kg (12.1lb) Wiffletree1.79 kg (3.9lb) Rocker bearing (x2) 3.62kg (8.0lb) Al bearing runner (x2) 0.80 kg (1.8lb) (optional) Strut blocks (x8)0.78kg (1.7lb) Cross bars (x2)1.38kg (3.0lb) Base total =28.43 kg (62.7lb) (excluding Al runners) 8 x Struts (total)4.11kg (9.1lb) Cage ring1.10 kg (2.4lb) Secondary mirror0.4 kg (0.9lb) Focuser (est)0.24kg (0.5lb) Spider (est)1.30kg (2.9lb) Viewfinder (est)0.45kg (1.0lb) Telescope total36.5kg (80.5lb)

Mirror Cell

Obsession 20” F/5 Mirror cell assembly

Babcock 24” F/4

22” F4.05 Design Secondary cage and spider assembly with baffling

Obsession 20” F/5 Truss tube clamps

Obsession 20” F/5 Inserting mirror

16” F/3.75 String Telescope Base

22” F4.05 Design Cutaway of bottom frame and drives

16” F/3.75 String Telescope In car!

Extras - Other Designs Internet a great source of information providing inspiration! Ultra-light designs evolving from more traditional Obsession MMT uses best features of all these designs

Sayre 22 inch CAD drawings

Dan Gray 16” F/3.75 Completed scope

16” F/3.75 String Telescope Disassembled scope (fits in a hatchback!)

Gary Wolanski, USA 16” F/5 Dobsonian, 40 Pound, all-metal construction

Jaques Civetta, France 465mm Dobsonian, fibreglass construction

Doug Tanaka, USA 12.5” F/6 String-Truss Dobsonian